The objectives of this study are to examine the effects of a prostaglandin synthase inhibitor on uterine and umbilical blood flow, maternal and fetal heart rates, arterial and venous pressure, and arterial gases in sheep. Chronically instrumented pregnant Dorset sheep at 115-135 days gestation are used. Under ketamine infusion, electromagnetic flow transducers are applied to the main uterine artery of the pregnant horn and to the common intra-abdominal vein. Polyvinyl catheters are placed in the maternal aorta, fetal aorta, maternal inferior vena cava, fetal vena cava, and in the amniotic cavity. After a minimum of 72 hours to allow for recovery and to reestablish maternal and fetal homeostasis, the test drug is infused into the maternal and fetal inferior vena cava using a range of doses.